Add support for angled, double quotes

The flag `HTML_SMARTYPANTS_ANGLED_QUOTES` combined with `HTML_USE_SMARTYPANTS` configures rendering of double quotes as angled left and right quotes (« »).

The SmartyPants documentation mentions a special syntax for these, `<<>>`, a syntax neither pretty nor user friendly.

Typical use cases would be either or, or combined, but never in the same document. As an example would be a person from Norway; he has a blog in both English and Norwegian (his native tounge); he would then configure Blackfriday to use angled quotes for the Norwegian section, but keep them as reqular double quotes for the English.

If the flag `HTML_SMARTYPANTS_ANGLED_QUOTES` is not provided, everything works as before this commit.

html.go

@@ -39,6 +39,7 @@ const (
 	HTML_USE_SMARTYPANTS                      // enable smart punctuation substitutions
 	HTML_SMARTYPANTS_FRACTIONS                // enable smart fractions (with HTML_USE_SMARTYPANTS)
 	HTML_SMARTYPANTS_LATEX_DASHES             // enable LaTeX-style dashes (with HTML_USE_SMARTYPANTS)
+	HTML_SMARTYPANTS_ANGLED_QUOTES            // enable angled double quotes (with HTML_USE_SMARTYPANTS) for double quotes rendering
 	HTML_FOOTNOTE_RETURN_LINKS                // generate a link at the end of a footnote to return to the source
 )
 

inline_test.go

@@ -798,3 +798,27 @@ func TestFootnotesWithParameters(t *testing.T) {
 
 	doTestsInlineParam(t, tests, EXTENSION_FOOTNOTES, HTML_FOOTNOTE_RETURN_LINKS, params)
 }
+
+func TestSmartDoubleQuotes(t *testing.T) {
+	var tests = []string{
+		"this should be normal \"quoted\" text.\n",
+		"<p>this should be normal &ldquo;quoted&rdquo; text.</p>\n",
+		"this \" single double\n",
+		"<p>this &ldquo; single double</p>\n",
+		"two pair of \"some\" quoted \"text\".\n",
+		"<p>two pair of &ldquo;some&rdquo; quoted &ldquo;text&rdquo;.</p>\n"}
+
+	doTestsInlineParam(t, tests, 0, HTML_USE_SMARTYPANTS, HtmlRendererParameters{})
+}
+
+func TestSmartAngledDoubleQuotes(t *testing.T) {
+	var tests = []string{
+		"this should be angled \"quoted\" text.\n",
+		"<p>this should be angled &laquo;quoted&raquo; text.</p>\n",
+		"this \" single double\n",
+		"<p>this &laquo; single double</p>\n",
+		"two pair of \"some\" quoted \"text\".\n",
+		"<p>two pair of &laquo;some&raquo; quoted &laquo;text&raquo;.</p>\n"}
+
+	doTestsInlineParam(t, tests, 0, HTML_USE_SMARTYPANTS|HTML_SMARTYPANTS_ANGLED_QUOTES, HtmlRendererParameters{})
+}

smartypants.go

@@ -205,13 +205,13 @@ func smartDashLatex(out *bytes.Buffer, smrt *smartypantsData, previousChar byte,
 	return 0
 }
 
-func smartAmp(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
+func smartAmpVariant(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte, quote byte) int {
 	if bytes.HasPrefix(text, []byte(""")) {
 		nextChar := byte(0)
 		if len(text) >= 7 {
 			nextChar = text[6]
 		}
-		if smartQuoteHelper(out, previousChar, nextChar, 'd', &smrt.inDoubleQuote) {
+		if smartQuoteHelper(out, previousChar, nextChar, quote, &smrt.inDoubleQuote) {
 			return 5
 		}
 	}
@@ -224,6 +224,14 @@ func smartAmp(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text
 	return 0
 }
 
+func smartAmp(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
+	return smartAmpVariant(out, smrt, previousChar, text, 'd')
+}
+
+func smartAmpAngledQuote(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
+	return smartAmpVariant(out, smrt, previousChar, text, 'a')
+}
+
 func smartPeriod(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
 	if len(text) >= 3 && text[1] == '.' && text[2] == '.' {
 		out.WriteString("…")
@@ -323,18 +331,26 @@ func smartNumber(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, te
 	return 0
 }
 
-func smartDoubleQuote(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
+func smartDoubleQuoteVariant(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte, quote byte) int {
 	nextChar := byte(0)
 	if len(text) > 1 {
 		nextChar = text[1]
 	}
-	if !smartQuoteHelper(out, previousChar, nextChar, 'd', &smrt.inDoubleQuote) {
+	if !smartQuoteHelper(out, previousChar, nextChar, quote, &smrt.inDoubleQuote) {
 		out.WriteString(""")
 	}
 
 	return 0
 }
 
+func smartDoubleQuote(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
+	return smartDoubleQuoteVariant(out, smrt, previousChar, text, 'd')
+}
+
+func smartAngledDoubleQuote(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
+	return smartDoubleQuoteVariant(out, smrt, previousChar, text, 'a')
+}
+
 func smartLeftAngle(out *bytes.Buffer, smrt *smartypantsData, previousChar byte, text []byte) int {
 	i := 0
 
@@ -352,8 +368,13 @@ type smartypantsRenderer [256]smartCallback
 
 func smartypants(flags int) *smartypantsRenderer {
 	r := new(smartypantsRenderer)
-	r['"'] = smartDoubleQuote
-	r['&'] = smartAmp
+	if flags&HTML_SMARTYPANTS_ANGLED_QUOTES == 0 {
+		r['"'] = smartDoubleQuote
+		r['&'] = smartAmp
+	} else {
+		r['"'] = smartAngledDoubleQuote
+		r['&'] = smartAmpAngledQuote
+	}
 	r['\''] = smartSingleQuote
 	r['('] = smartParens
 	if flags&HTML_SMARTYPANTS_LATEX_DASHES == 0 {